green enchilada sauce - homemade necessary or out of a jar ok?

The time honored principle of "fast, cheap, good: pick two" applies here. Basically with jarred or canned foods you are trading convenience for quality.

Amusingly I recently watched an episode of America's Test Kitchen where they taste tested jarred pasta sauces. The winning sauce and other high scoring sauces ended up being expensive.

If I really had to buy jarred enchilada sauce I'd probably look for something locally produced. I'd balk at buying something nationally distributed. As a Californian, there are some options here. If I recall correctly, at least one vendor at my town's farmers market has sold this type of item in the past.

It's really your call whether or not you think jarred enchilada sauce is adequate but I note that the local mom-and-pop taquerias here make their own from scratch.

I have no recommendations concerning national brands of jarred sauce but you may want to consider the more expensive products if taste is important.

One thing about making this from scratch is you know what is goes into it. Commercial producers often load up their products with sugar and salt to make them more appealing to the typical American consumer.

Anyhow your taste buds, your time, your wallet, your call.

Best of luck.

Here are a few general suggestions for buying commercial packaged products new to you.
* Avoid, as much as possible, those with large components of sugar, salt and preservatives. Some quantity of each is needed, but heavy amounts don't let the taste of the chilis come through, and aren't very healthy.
* Avoid cans if, like drbabs, you find they give an unpleasant taste. Otherwise, one of the greatest inventions since persevering/drying and salting foods. Until sliced bread, of course. There are also products packaged in glass and in airtight bags.
* If you have a great local store, ask the proprietor and/or manager of that section which they have tasted, which sell best, which have ever been returned and why. With those answers, you can make a more informed choice.
* If buying online, look for top consumer ratings and brands you may know from other products. Pay less attention to the items promoted by the site.
When in doubt, buy a small package. Usually these are more expensively priced, but for a first time, small is better. What if you don't like it?

I live in Austin where peppers and tomatillos are plentiful year round, so I’d make it from scratch. But if my only choice were canned vegetables, like you, I’d be tempted to buy the jarred stuff. I have no experience with any brands, but in general, I tend to avoid foods in cans (except maybe tomatoes) because they always taste metallic to me. If you do buy a prepared sauce, taste it before using it, and add to it to your taste. Like I always think food needs more acid, so I’d be likely to add a little lime juice. If you can eat cilantro, some fresh cilantro will probably enhance it, too,